Chemical looping: a decarbonization landmark

Posted: June 02, 2025

In Baton Rouge, Louisiana, construction is currently underway for a hydrogen plant that expects to make a difference. The operators, Babcock & Wilcox, claim that they will be producing 10 to 15 tons of carbon-negative hydrogen from biomass by 2029.

Hydrogen production currently faces challenges in terms of emissions intensity (for fossil-fuel-based “grey” hydrogen) and affordability (renewable-electricity-based “green” hydrogen). By using its patented BrightLoop technology, Babcock & Wilcox has found a way to integrate carbon capture into the energy production process, thus reducing unused waste while vastly improving efficiency. BrightLoop uses a technique called chemical looping to separate a nearly pure stream of hydrogen from oxygen, with the resultant carbon dioxide isolated for capture and storage or reuse.

At Baton Rouge, the firm projects it will be able to produce green hydrogen at a price point competitive with grey hydrogen. If it succeeds, it will represent a major milestone in the development and deployment of chemical looping—a technique decades in the making that may now help decarbonize electricity generation, hydrogen production, and more.

What is chemical looping?

“Chemical looping” refers to techniques that use a solid carrier material to move oxygen—or occasionally another compound like carbon dioxide—between parts of a system, enabling a controlled continuous cycle of reactions.

The most elemental of these techniques, chemical looping combustion (CLC), involves two different reactors. In the first, an oxygen carrier (typically a metal oxide like iron oxide) provides oxygen that reacts with carbonaceous feedstocks, producing a concentrated stream of carbon dioxide—which then gets captured—as well as heat. In the second, that now-depleted oxide gets exposed to air or steam, thus regenerating its oxygen so it can be reintroduced to the first reactor. As the metal oxide cycles through the system, it gets continuously oxidated and reduced.

What results is an efficient low-carbon method for converting natural gas, coal, and biomass into useful products such as electricity—or, with the addition of an extra reactor as in the BrightLoop system, hydrogen. Chemical looping reforming (CLR) and gasification (CLG) refer to processes that cyclically deploy metal oxide carriers to produce syngas, and thus potentially hydrogen, from gaseous or solid carbonaceous feedstocks. The energy-intensive process of air separation is not required for oxygen inputs, unlike in other techniques; carbon dioxide need not be emitted into the atmosphere and can, instead, be captured for storage or reuse.

Chemical looping was pioneered at Ohio State University by Liang-Shih Fan, who argued that its full implementation could capture at least 95% of the carbon dioxide emitted from coal combustion power plants. A 2017 paper by Fan's team demonstrated an approach using iron oxide as a carrier that used shale gas to generate heat for powering turbines while producing a concentrated stream of pure carbon, which could partially substitute for methane in syngas production via steam reforming.

“In the simplest sense, combustion is a chemical reaction that consumes oxygen and produces heat,” Fan said. “Unfortunately, it also produces carbon dioxide […] So, we use a method for releasing the heat without combustion. We carefully control the chemical reaction so that the feedstock never burns—it is consumed chemically, and the carbon dioxide is entirely contained inside the reactor.”

One crucial element of the process is the oxygen carrier, which must be able to move through different oxidation states at feasible temperatures. It also needs the capacity to do so many times over without deteriorating, a factor that Fan’s team was eventually able to achieve. In 2021, after decades of research, a chemical looping technique they developed was licensed to Babcock & Wilcox.

Advancements and adoption of chemical looping technology

Gradually, chemical looping techniques—in combustion, reforming, and gasification—are gaining in practicability. Babcock & Wilcox, who plan to open three chemical looping-based hydrogen plants by 2028, are betting on the technology’s scalability with flexible feedstocks.

In 2022, researchers from the Technische Universität in Graz and the start-up Rouge H2 Engineering succeeded in using a chemical looping process to generate high purity hydrogen from biogas at their demonstration plant in Mureck, southern Austria. The following year, partners in the EU initiative CLARA announced that they had successfully demonstrated their biomass gasification processes at a pilot at Darmstadt. Lead researcher Bernd Epple, who now works on the EU-funded Project Coral, argued that scaling up was possible and commercialization would be likely by 2028. "It works," he said. "It's very robust.”

The following year, an international collaboration named CHEERS (Chinese-European Emission Reducing Solutions), which involved public bodies from the EU and China as well as TotalEnergies and Dongfang Boiler Group, announced that it was in the testing phase for the world’s largest CLC demonstration unit in Deyang City, China. This initiative applied chemical looping approaches to petroleum coke and lignite, targeting a 96% carbon capture rate. “Testing in the CHEERS demonstration unit,” the team reported in 2024, “showed that for solid fuels the CLC technology can provide high carbon capture efficiency at very low costs, indicating that the technology is commercially viable.”

These developments have benefited from sophisticated process modeling techniques. Researchers are able to use both experimental investigation, which generates data, and computational software that uses said data to enable simulations. Machine learning has been proposed as a low-cost method for predicting the range of hydrogen production within each looping cycle as well as the reaction performance of oxygen carriers. One of the aims of the CHEERS initiative was to deploy full-scale Computational Fluid Dynamics (CFD) simulations of the pilot and demonstration unit, a potentially advantageous approach considering that high temperatures and fluidized particles make it hard to make detailed measurements in a CLC unit.

Potential applications appear to be broad. Chemical looping can remove pollutants and improve process efficiency in chemical production via the targeted burning of one molecule from a mixture of combustibles. In a recent paper, researchers demonstrated a procedure that uses a bismuth oxide catalyst to combust small amounts of acetylene out of ethylene feedstocks, an important step to prevent the poisoning of polymerization catalysts while making polyethylene plastics.

The bismuth oxide catalyst has made a difference by providing its own oxygen during combustion. “We were able to take oxygen out of the catalyst and put it back in multiple times, where the catalyst changes slightly, but its reactivity is not impacted,” explained Matthew Jacob, one of the researchers, who also noted that chemical looping allowed his team to control the concentration and reactivity of the oxidant.

Back at Ohio State University, the innovations with chemical looping technology continue. One recent breakthrough—which built on Fan’s prior research—uses chemical looping gasification to more efficiently and safely produce high-quality syngas out of materials like plastics and agricultural waste. In a recent paper, Ishani Karki Kudva and her team argue that their CLG system could offer carbon emission reductions of up to 45% compared to conventional processes—all while producing syngas with purity five to ten percentage points higher than that generated otherwise. Kudva has stated that the team’s next priority is expanding the process to include municipal solid waste from recycling centers. “The work in the lab is still going on with respect to commercializing this technology and decarbonizing the industry,” she said.